Clinical electrophysiologic study of antiarrhythmic properties of flecainide: Acute intraventricular delayed conduction and prolonged repolarization in regular paced and premature beats using intracardiac monophasic action potentials with programmed stimulation

Abstract

Flecainide acetate is one of the few antiarrhythmic drugs that substantially delay myocardial repolarization in tissue preparations. The potential clinical benefit of this mechanism stimulated our study of the acute effects of this agent on intraventricular conduction and repolarization in man. Thus three normals and six patients were studied before and after an intravenous dose of 2 mg of flecainide/kg. We determined ventricular effective refractory period (VERP) and recorded monophasic action potentials (MAP) from the right ventricle during induction of ventricular ectopic beats with coupling intervals of VERP +1, +30, +40, and +50 msec. Flecainide induced significant prolongations of MAP (+9.6%, p < 0.01) and VERP (+9.8%, p < 0.05) during regular pacing, as well as delayed intraventricular conduction time (+16.8%, p < 0.05). The MAP of the earliest inducible ventricular ectopic beat was even more markedly prolonged (+19.0%, p < 0.001) and at coupling intervals 30 to 50 msec longer than VERP such considerable prolongation remained (+14.2%, p < 0.001). In addition, this study illustrates the utility of the MAP ventricular recording method, combined with programmed ventricular stimulation, in demonstrating clinical electrophyslologic properties directly comparable with those of microelectrode investigations.